Air cleaners or dust collector devices sometimes use exhaust gas from a valve and pressure tank (reservoir) to back flush filters. Examples of such air filters assemblies are disclosed in, for example, U.S. Pat. Nos. 6,090,173; 4,218,227; 4,395,269; 5,980,598; 6,322,618; DE 3905113; and Patent Publication U.S. 2006/0112667A1, each of these patent documents being incorporated by reference herein.
Effective cleaning of these filters requires that the exhaust jet fill the opening of the filter to be cleaned. In many implementations, the opening of the filter corresponds to the opening in the tubesheet, in which the filter is mounted. Improvements in pulse cleaning filters are desirable.